Kezo it is a dilemma and a gamble, whether to wait 7 weeks to see if Hyundai and MB decide to bring on the AWD in Q1, as Hyundai must be finding a big interest in the I6 at that AP and hopefully they may be tempted to expand that to include the AWD model.
If you think that the I6 RWD would meet your needs, you could always order it and if the AWD comes on at a reasonable AP in Q1, you could always change over your order.
Unfortunately as we have seen with our fellow members who fancied the BMW i4 and Skoda Enyaq, MB is a bit like an auction and it is all to easy to miss out on what you fancied.